The Dimensional Portal is a vortex that functions as a gate in order to allow travel between Aernas, Elyos, and the Underworld. Demons have used it in the past to cross over to Aernas and assault that world, while Kounatians and the moderate demons who aided humans have made countless attempts to seal them. Demons in Elyos must traverse through Trivia in order to access the portal to Aernas.
Though initially only existing between Aernas and Elyos, the Underworld's dimensional barriers have also recently been affected due to the breaking of the seals that separated Aernas from Elyos, weakening them and allowing travel to become possible.
Several characters are also known to be able to manipulate the dimensional fabric in order to create portals. Kaze'aze can create dimensional rips to transport her enemies into the unknown, and one of her attacks also consists of forcefully warping the player in and out of a vortex to deal damage; this is also shared with Dio's and Ley's grab. Dio can also use Life Keep to stash a portion of his health into another dimension, which returns to him when he is incapacitated. Kassias Grandiel, possibly utilizing the power of the Klara Libri's clone, opened a Dimensional Portal that led to the Underworld's Monster Train 301. Berkas also opened a portal in order to escape from the Underworld and into the deserts of Alcubra.
The portal is only seen in the Relics of Kounat, where Dio attempts to seal it. However, the portal cannot be destroyed until the Assassin Champion, the Mini Boss from the fourth wave, is defeated. No MP will be gained from attacking it. It also has no attacks, and does not actually do anything.
The Upper Dimensional Portal will lead to a map that has many platforms but short horizontal distance. There is enough height to avoid Drawl's fire stream but not enough room to avoid Veron's multiple blasts of energy from above.
The Lower Dimensional Portal will lead to a map that has long horizontal distance but three platforms. There is enough room to avoid Veron's multiple blasts of energy but not enough height to avoid Drawl's fire stream.
A dimensional portal exists in Ancient Golem Ruins and Dimension's End, which Veigas uses to reach Aernas. A massive dimensional portal is also created in the aftermath of the battle between the Twelve Disciples and Veigas.
- Hell Bridge most likely hosts a Dimensional Portal as Gardosen, a demonic figure, was being pulled into Aernas.
- According to a Brazilian article, magic crystals were used to stabilize the portals in the Relics of Kounat on the Aernas side, and that destroying those crystals were what destroyed the portals.